Go 学习之路：Println 与 Printf 的区别

Println 和 Printf 都是 fmt 包中公共方法；在需要打印信息时常用的函数，那么二函数有什么区别呢？

附上代码

package main

import (
	"time"
	"fmt"
)

const (
	Man = 1
	Female = 2
)

func main(){
	timer := time.Now().Unix()
	if(timer % Female == 0){
		fmt.Println("%d is Female", timer)
		fmt.Printf("%d is Female", timer)
	}else{
		fmt.Println("%d is Man", timer)
		fmt.Printf("%d is Man", timer)
	}
}

运行结果

%d is Man 1529049077 // println输出结果
1529049077 is Man // printf输出结果

结果可知

Printf : 可打印出格式化的字符串,Println 不行；

稍做修改下

package main

import "fmt"

const (
	StrN = "123"
	IntN = 123
)

func main(){
	fmt.Println(StrN)
	fmt.Printf("%s\n",StrN)
	fmt.Printf(StrN)
	fmt.Println(IntN)
	fmt.Printf("%d\n",IntN)
	fmt.Printf(IntN)
}

结果

cannot use IntN(type int) as type string in argument to fmt.Printf

原因

// Println formats using the default formats for its operands and writes to standard output.
// Spaces are always added between operands and a newline is appended.
// It returns the number of bytes written and any write error encountered.
func Println(a ...interface{}) (n int, err error) {
	return Fprintln(os.Stdout, a...)
}


// Printf formats according to a format specifier and writes to standard output.
// It returns the number of bytes written and any write error encountered.
func Printf(format string, a ...interface{}) (n int, err error) {
	return Fprintf(os.Stdout, format, a...)
}

总结一句话： println 会根据你输入格式原样输出，printf 需要格式化输出并带输出格式；